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Engine Room Temperature and Batteries


Simon (Hawksmoor)

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Hawksmoor is a semi-trad with a Beta Marine engine mounted below the deckboards which are sound insulated (and hence thermally insulated).

The batteries live on a shelf off to one side.

We have recently put a digital thermometer on top of the battery bank and recorded ambient air temperatures of 44 to 46 degrees C

Googling "Max temp for lead acid batteries" suggests a max temp of 50 degrees C

I would imagine that this setup is pretty much what most boats have (maybe without the insulation). Has anybody else measured temperatures "down below"?

Any thoughts as to whether these sorts of temperatures might hurt the batteries or shorten their life?

 

 

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An answer I gave elsewhere about 2 months ago also for a semi-trad with sound insulation:

 

I would be more concerned about the alternators if you use high current devices when the engine is running but after the temperature has reached maximum. I expect the engine alternator will be OK because after half an hour or so it will have virtually shut down unless you have a fault. The domestic alternator that may be subject to high loads at any time is different. The amount of heat transferred depends upon the temperature difference between the air and the alternator parts so on your figurers you only have a bit over 20 degrees difference so cooling must be compromised. If that really is the ambient air temperature in the engine bay and not something that has been heated by radiation or conduction then I would also be concerned about the efficiency of the combustion in the engine. I wonder how well the engine bay is vented? At 1500 rpm a 1.5 litre engine will consume about 900 litres of air a minute at 80% volumetric efficiency. Even on a hot day that would help keep the actual engine area cooler. This is why I question the true ambient air temperature in the bay. I have no data on the maximum battery temperature allowed but apart from potentially increasing the water consumption to some degree and maybe causing stress in the plates by expansion I doubt it will do significant harm. If any readers are battery experts please respond

I have been doing further research and found it stated that for every 8C above 25C a lead acid battery is operated at it halves the design life of the battery. This is caused by an exponential increase in corrosion of internal parts. I think that you need to double check that the ambient engine room temperature, then ensure at least a minimum of a 3" X 3" vent into the engine bay. If that does not reduce the ambient temperature closer to 25C then move the batteries into one or both side lockers/seats, possibly with thermal insulation under them.

The above is not a bad as it may seem. That "rule" probably only fully applies when the battery is operated above 25C for the whole of its design life. If you think about it unless you are a very keen long distance cruiser your batteries will only be above 25C for a small fraction of their life so I suspect any reduction of life will not be noticeable when other things like sulphation,  excessively deep discharge, and daily cycling are also contributing to reduced life.

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46 minutes ago, Simon (Hawksmoor) said:

Hawksmoor is a semi-trad with a Beta Marine engine mounted below the deckboards which are sound insulated (and hence thermally insulated).

The batteries live on a shelf off to one side.

We have recently put a digital thermometer on top of the battery bank and recorded ambient air temperatures of 44 to 46 degrees C

Googling "Max temp for lead acid batteries" suggests a max temp of 50 degrees C

I would imagine that this setup is pretty much what most boats have (maybe without the insulation). Has anybody else measured temperatures "down below"?

Any thoughts as to whether these sorts of temperatures might hurt the batteries or shorten their life?

 

 

When I worked Offshore the start batteries for out Caterpillar generators were mounted beside the engines. These were 2 X 350 KW sets in quite a large engine room. The temperature was quite warm even in winter and the starter batteries definitely didn't like it. We use to have a battery specialist come out to test different batteries and he was horrified we ran them that warm, it definitely shortened their life

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In cars, alternators and lead acid batteries are operated in high temperature conditions. The air passing through the radiator is heated up to temperatures that can reach 80C plus and the temperature around the engine can approach this when stuck in a traffic jam. Electronics to work in an engine bay are designed to cope with higher temperatures than normal because of this. As Tony says, many heat activated processes that lead to deterioration roughly double for every 8 to 10C temperature rise (Arrhenius equation). The alternator and batteries in the engine bay should be able to cope with quiet high temperatures by design, but if it is possible to reduce it, then it is a good idea. Never measured the air temperature inside the engine hole in my boat, but I wouldn't be surprised if it is around 40C or so with the engine running. Certainly the cat used to like sitting on the warm deck board once the engine was stopped and we were moored up! My starter and house batteries are all down there with the engine.

Jen

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I was expecting a question for temperatures at to opposite end of the range!

When I first fitted my set of Trojanoids in the back cabin, this coincided with the start of a long cold winter and the temp in the back cabin was often 0c and rarely rose above about 6c for several months. I suspect this is another factor which lead to their rapid sulphation and capacity reduction. My Sterling Pro Ultra charger has temperature compensation but not enough.

So the OP and others reading the thread title should perhaps be equally concerned about low temperatures in the battery compartment unless they are on a permanent shoreline. 

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Mine are under the bed which is next door to the engine space. They're in boxes with vent tubes on the top leading up into the air cooled engines outlet cooling duct. I've just renewed the engine battery at 11 years old, cheap cabin battery 5 years old and still has about 70% capacity.

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My batteries are effectively in with the engine near to the hospital silencer which gives off a terrific amount of heat.  I do open the compartment door when it gets really hot but I suspect a lot of the time they are living at a temperature that is more than is good for them.  Conversely in the winter they spend months unattended at temperatures down to freezing.  

But they are coming up to eight years old now and still working efficiently.

I've given up with all the technicalities of electricity storage.  It's been said many times but solar power has effectively solved most of the problems involved in maintaining a decent electricity supply, and if you buy really good quality batteries eg Trojans all you really need to worry about is keeping the levels topped up.    

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Beats me why the batteries on most wide beam boats are stuffed down there next to the engine, often having large steel deck plates above. The heat with the engine running and sun beating down on the deck plating is quite severe.  There are usually big lockers on the back of wide beams, often just full of rubbish where the batteries could be, cooler and get atable.

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On 10/08/2017 at 10:39, Neil2 said:

My batteries are effectively in with the engine near to the hospital silencer which gives off a terrific amount of heat.  I do open the compartment door when it gets really hot but I suspect a lot of the time they are living at a temperature that is more than is good for them.  Conversely in the winter they spend months unattended at temperatures down to freezing.  

But they are coming up to eight years old now and still working efficiently.

I've given up with all the technicalities of electricity storage.  It's been said many times but solar power has effectively solved most of the problems involved in maintaining a decent electricity supply, and if you buy really good quality batteries eg Trojans all you really need to worry about is keeping the levels topped up.    

 

A few of us here would disagree strongly with this!

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In general - if you keep engines and batteries 'cool' they'll last longer and the latter use less water. If they're cocooned, I'd suggest you introduces some forced air ventilation - such as a couple of old style mainframe computer fans. They take very little power.

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1 hour ago, Simon (Hawksmoor) said:

Hawksmoor is a semi-trad with a Beta Marine engine mounted below the deckboards which are sound insulated (and hence thermally insulated).

The batteries live on a shelf off to one side.

We have recently put a digital thermometer on top of the battery bank and recorded ambient air temperatures of 44 to 46 degrees C

Googling "Max temp for lead acid batteries" suggests a max temp of 50 degrees C

I would imagine that this setup is pretty much what most boats have (maybe without the insulation). Has anybody else measured temperatures "down below"?

Any thoughts as to whether these sorts of temperatures might hurt the batteries or shorten their life?

How well lagged is your exhaust?  This prob releases more heat into the engine bay if poorly lagged than the engine.   You could also add forced ventilation with the intake low and the outtake high.   I'm doing this, but I have a number of electrical items in my engine room as well.   On reading up the outtakes should be near the items that cause the heat, whilst the intakes should be low and away from them.  Outtake ventilation is around 110% of intake flow to count for the heat expansion of the air.

Edited by Robbo
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On 10/08/2017 at 11:04, OldGoat said:

In general - if you keep engines and batteries 'cool' they'll last longer and the latter use less water. If they're cocooned, I'd suggest you introduces some forced air ventilation - such as a couple of old style mainframe computer fans. They take very little power.

 

I'd say some whopping big fans would be needed to push the volumes of air through to cool a whole engine bay.

Power consumption will be of no concern as only in use when the engine is running.

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23 minutes ago, Mike the Boilerman said:

 

I'd say some whopping big fans would be needed to push the volumes of air through to cool a whole engine bay.

Power consumption will be of no concern as only in use when the engine is running.

If I'd said 'whopping big' fans everybody would run for cover! I have a pair of 8" computer server fans that blast cool air over everything and cost very little at the time. There are still (I think) computer junkshops where you can pick them up for little cost. Usually 24v - but you can run them off 12v.

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53 minutes ago, Mike the Boilerman said:

 

I'd say some whopping big fans would be needed to push the volumes of air through to cool a whole engine bay.

Power consumption will be of no concern as only in use when the engine is running.

Agreed.

We have engine bay and bilge blowers fitted to our boat.

When we had a few hot days earlier this year we checked out if running the fans made any difference to the engine bay temperature which was reading from memory about 38 degrees with the engine running. It made bugger all difference at all.

Our engine bay at this time of year very rarely gets below 25 degrees and with the engine running is usually in the low 30's. Even in the winter when we have the diesel heating running the waste heat from that heats the engine bay to above 25 degrees. The only time it gets below that sort of temperature is mid week when we are at home during the winter months, but even then we heat the engine bay so it is usually above 10 degrees.

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4 minutes ago, Neil2 said:

As regards using fans/blowers to cool the engine bay, isn't it better to, ahem, suck rather than blow..?

Ours do suck as they are designed to remove vapours from the engine bay and bilges.

They still make bugger all difference.

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1 hour ago, Mike the Boilerman said:

 

I'd say some whopping big fans would be needed to push the volumes of air through to cool a whole engine bay.

Power consumption will be of no concern as only in use when the engine is running.

I use one 100 MM fan Blowing cold Air down through a Mushroom Vent terminating one Metre from Floor level and another 100 MM pushing out to another Mushroom at Cabin Roof height,both can be Switched manually or they will Power up at 30 Degrees C by means of a Temperature sensor.

6 Foot 6" full Height Engine Room. 

 

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3 hours ago, bizzard said:

Non electric engine space cooling. Keep fit, practice your rowing.  Change tunnel exhaust outlet for engine space outlet.

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Oh my God.......they found Tom..!

Edited by Neil2
brainfart
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